System and methods for detecting, monitoring, and removing deposits on boiler heat exchanger surfaces using vibrational analysis

ABSTRACT

A boiler system includes a boiler having at least one heat exchanger having a surface on which a deposit may form. The boiler system further includes at least one retractable sootblower having a lance tube for carrying a high pressure fluid into the boiler. The lance tube is configured such that the high pressure fluid impacts the heat exchanger surface to effect a vibration thereof. The boiler system also includes at least one vibration measuring device coupled to the boiler system. The vibration measuring device is configured to measure the vibration of the heat exchanger surface, and the measured vibration indicates presence or absence of the deposit on the heat exchanger surface. The vibration measuring device may optionally detect a vibration caused by the release of the deposit from the surface of the heat exchanger or the impact of the released deposit with a surface in the boiler system.

FIELD

The present invention relates generally to fouling or ash deposits inboilers and, more particularly, to a system and methods for detecting,monitoring, measuring, and/or removing the deposits on heat exchangersof the boilers by using vibrational monitoring and analysis.

BACKGROUND

In the paper-making process, chemical pulping yields black liquor as aby-product. Black liquor contains inorganic cooking chemicals along withlignin and other organic matter that separates from wood during pulpingin a digester. The black liquor is burned in a boiler. The two mainfunctions of the boiler are to recover the inorganic cooking chemicalsused in the pulping process and to make use of chemical energy in theorganic portion of the black liquor to generate steam for a paper mill.As used herein, the term boiler includes a top-supported boiler thatburns a fuel that, in the process, fouls heat transfer surfaces.

An example of a boiler used to burn black liquor to generate steam is aKraft boiler. A Kraft boiler includes banks of heat exchangers atvarious levels in the furnace for extracting heat by radiation andconvection from the furnace gases to generate heated fluids such assteam. Typically, the furnace gases first interact with heat exchangersin a superheater bank to generate superheated steam. The furnace gasesthen interact with heat exchangers in a generating bank to generateworking steam. The generating bank may also be referred to as a boilerbank. Finally, the furnace gases interact with heat exchangers in aneconomizer bank, which generates lower temperature heated fluids. Thebanks of heat exchangers are constructed of an array of platens that areconstructed of tubes that function as heat exchanger surfaces forconducting and transferring heat. While operating, heat exchangersurfaces are continually fouled by ash generated in the furnace chamberfrom burning fuels such as black liquor. The amount of fuel that can beburned in a boiler is often limited by the rate and extent of fouling onthe surfaces of the heat exchangers. The fouling, including ashdeposited on the heat exchanger surfaces, reduces the heat absorbed fromfuel combustion, resulting in reduced exit steam temperatures in thefouled heat exchanger banks and high gas temperatures entering the nextheat exchanger bank in the boiler. For example, fouling in thesuperheater bank results in decreased steam temperatures exiting theheat exchanger and increased furnace gas temperature entering thegenerating bank. The heat exchanger surfaces in the generating bank tendto be relatively narrow compared to the spacing in the superheater andeconomizer banks, which increases the likelihood of fouling in thegenerating bank as compared to fouling in the superheater and economizerbanks.

Fouling can require a boiler to be shutdown for cleaning when either theexit steam temperature is too low for use in downstream equipment or thetemperature entering the downstream heat exchanger bank, such as thegenerating bank downstream from the superheater bank, exceeds themelting temperature of the deposits, resulting in gas side pluggage ofthe downstream bank. In addition, fouling can eventually cause pluggingin the upstream bank as well, such as the superheater bank. In order toremove the plugging from the heat exchanger banks, the burning processin the boiler must be stopped. Kraft boilers are particularly prone tothe problem of fouling in the generating bank with ash deposits thatmust be removed for efficient operation, however the other heatexchanger banks may also become fouled. Three conventional methods ofremoving ash deposits from the heat exchanger banks in boilers such asKraft boilers include: 1) sootblowing, 2) chill-and-blow, and 3)waterwashing. This application addresses only the first of thesemethods, sootblowing.

Sootblowing is a process that includes blowing deposited ashes off aheat exchanger surface that is fouled with ash deposits using blasts ofsteam from nozzles of a lance of a sootblower. Sootblowing is performedessentially continuously during normal boiler operation, withsootblowers in various locations in operation at different times.Sootblowing is usually carried out using steam. The steam consumption ofan individual sootblower is typically 2-3 kg/s, and as many as foursootblowers may be operated simultaneously. Typical sootblower usage isabout 3-7% of the steam production of the entire boiler. Thus, thesootblowing procedure consumes a large amount of thermal energy producedby the boilers being cleaned.

A typical sootblowing process utilizes a procedure known as sequencesootblowing, wherein sootblowers operate at predetermined intervals andin a predetermined order. The sootblowing procedure runs at this paceirrespective of the amount of fouling that may occur at any particularlocation in the heat exchanger. Often, this leads to plugging in areasof the heat exchanger that are insufficiently cleaned by thepredetermined sootblowing sequence that cannot necessarily be preventedeven if the sootblowing procedure consumes a high amount of steam. Eachsootblowing operation reduces a portion of nearby ash deposits, but ashdeposits that are not completely removed may nevertheless continue tobuild up over time. As ash deposits grow, sootblowing becomes graduallyless effective and impairs heat transfer. When an ash deposit reaches acertain threshold where boiler efficiency is significantly reduced orcombustion gases cannot be removed from the furnace, deposits may needto be removed by another cleaning process requiring the boiler to beshut down.

SUMMARY

It is desirable to use the total energy of the high pressure steam ofthe sootblowers to induce vibration on the heat exchanger surfaces. Thevibration of the heat exchanger surfaces is then used to detect,monitor, measure, and/or remove ash deposits from the heat exchangersurfaces of boilers and, as a result, conserve energy by having thesootblowers use a minimum amount of steam. It is also desirable todevelop a map of the ash deposits deposition pattern surrounding each ofthe sootblowers so that the information in the map may be used to adjustpriority of sootblower operations for efficient use and, in general, todevelop an effective sootblowing strategy.

An aspect of the invention is directed to a boiler system that includesa boiler having at least one heat exchanger, the at least one heatexchanger having a surface on which a deposit may form. The boilersystem further includes at least one retractable sootblower having alance tube for carrying a high pressure fluid into the boiler. The lancetube is configured such that the high pressure fluid impacts the heatexchanger surface to effect a vibration thereof. The boiler system alsoincludes at least one vibration measuring device coupled to the boiler,the vibration measuring device being configured to measure the vibrationof the heat exchanger surface. The measured vibration of the heatexchanger surface indicates presence or absence of the deposit on theheat exchanger surface.

Another aspect of the invention is directed to a method of detecting adeposit on at least one heat exchanger surface of a boiler that includesmoving a sootblower lance tube relative to the at least one heatexchanger surface and impacting the at least one heat exchanger surfacewith steam discharged from the lance tube. The method further includesmeasuring a vibration at a location on the boiler caused by the impactof the steam with the at least one heat exchanger surface and analyzingthe measured vibration to detect the presence of the deposit at thelocation.

Another aspect of the invention is directed to methods of mapping thelocation deposits in a boiler system. The method includes identifyingthe location of a deposit on a heat exchanger surface based on reactiveforces generated by impacting deposits with a high pressure fluiddischarged from a sootblower. A deposit map may then be generated basedon the positions of the identified deposits.

Another aspect of the invention is directed to a method of detecting adeposit released from a heat exchanger surface in a boiler. The methodincludes providing at least one vibration measuring device coupled tothe boiler and detecting a vibration caused by at least one of therelease of a deposit from a surface of a heat exchanger or the impact ofa released deposit with a surface in the boiler, the vibration beingdetected by the vibration measuring device. The method further includesanalyzing the detected vibration to determine a location on the surfaceof the heat exchanger surface from which the deposit was released.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate various embodiments of theinvention and, together with a general description of the inventiongiven above and the detailed description of the embodiments given below,serve to explain the embodiments of the invention.

FIG. 1 is a schematic illustration of a boiler system in accordance withan embodiment of the invention;

FIG. 2 is an enlarged detail of top perspective view of a portion of theboiler system shown in FIG. 1 illustrating a number of accelerometerspositioned on hanger rods supporting a number of platens;

FIG. 3 is a top perspective view of two heat exchanger tubular surfaces,which, for the sake of clarity, are represented by platens in FIG. 2,illustrating two sootblower lance tubes positioned between the heatexchanger tubular surfaces;

FIG. 4 is a flow chart illustrating a process for analyzing signals froma vibration measuring device to identify the presence of deposits inaccordance with an embodiment of the invention; and

FIG. 5 shows exemplary tracings from data collected during the operationof a boiler system in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic illustration of a boiler system 10 having a boiler12 including a plurality of heat exchangers 22 with deposits 20 formedthereupon, one or more vibration measuring devices 14, a sootblower 16,a deposit detection device 18, and an integrated device 30.

For the purposes of the present invention, the term “boiler” 12 refersto a closed vessel in which water or other fluid is heated in heatexchangers that are contacted by hot gases from a combusted fuel. Anexemplary boiler 12 is a recovery boiler. The heated or vaporized fluidexits the boiler 12 for use in various processes or heatingapplications, including boiler-based power generation, process heating,and the like. The term “recovery boiler” includes the type of boiler 12that is part of the Kraft process of pulping where chemicals for pulpingare recovered and reformed from black liquor, which contains lignin(among other organic materials) from previously processed wood. Theblack liquor is burned, generating heat, which is usually used in theprocess or in making electricity, much as in a conventional steam powerplant. The two main functions of recovery boilers are to recover theinorganic cooking chemicals used in the pulping process and to use thechemical energy in the organic portion of the black liquor to generatesteam for the mill. A detailed description of Kraft black liquor boilersare described in detail in U.S. Pat. Nos. 6,323,442 and 7,341,067, whichare incorporated by reference herein in their entireties.

With reference to FIGS. 2 and 3, the boiler 12 comprises a series ofheat exchangers 22. The heat exchangers 22 may be organized into asuperheater bank, a generating bank, an economizer bank, andcombinations thereof The heat exchangers 22 are formed of tubes (FIG. 3)or platens (FIG. 2) having surfaces 48. Each heat exchanger 22 maycomprise approximately 20-100 tubes, for example. The heat exchangersurfaces 48 have passages 50 upstream and/or downstream therethrough toallow a sootblower 16 to move relative to the heat exchanger surfaces48, as will be described in greater detail below.

In an embodiment, the boiler 12 is suspended from a ceiling with boilersupporting structures that may include overhead beams 34 and hanger rods32. The overhead beams 34 may include I-beams. Approximately 30-100hanger rods 32 (FIG. 2) may be used to suspend the boiler 12 from theoverhead beams 34. More specifically, the hanger rods 32 may be boltedor otherwise coupled to the overhead beams 34 at one end and coupled tothe heat exchangers 22 either directly or via headers 36 (FIG. 2) at anopposite end. The hanger rods 32 typically have a diameter that rangesfrom about 1 inch to about 3 inches and length range from about 2 feetto about 20 feet long.

As explained above during use, slag and/or ash deposits 20 may form onthe surfaces 48 of the heat exchangers 22, which degrades thermalperformance of the boiler system 10. The amount of the deposit 20 mayvary at different locations on the heat exchanger surfaces 48.

The boiler system 10 includes one or more sootblowers 16 for cleaningdeposits 20 from the heat exchanger surfaces 48. For example, a boilersystem 10 may include a plurality of sootblowers 16 spaced apart byapproximately 5-15 feet within the boiler 12. For the purposes of thepresent invention, the term “sootblower” 16 refers to an apparatus usedto project a stream of a high pressure fluid 24, such as steam, air,water or other fluid against heat exchanger surfaces 48 of large-scalecombustion devices, such as utility or recovery boilers. Generally, thesootblowers 16 include a lance tube 26 that is in fluid communicationwith a source (not shown) of high pressure fluid 24, such as steam.While the sootblowers 16 described herein utilize steam, it is notedthat the invention is not so limited, and the sootblowers 16 may alsouse other high pressure fluids 24. In embodiments of the invention, thehigh pressure fluid 24 may be supplied at a pressure of approximately100-400 psi. Each sootblower 16 also includes at least one nozzle 28 atthe distal end 29 of the lance tube 26 of the sootblower 16. In anembodiment, each sootblower 16 includes two nozzles 28 that are spaced180° apart at the distal end 29 of the lance tube 26.

As described in greater detail below, a retractable sootblower 16 isconfigured such that the lance tube 26 translates (i.e., periodicallyadvance and retract) in and out of an interior of the boiler 12 as thehigh pressure fluid 24 is discharged from the nozzles 28. The lance tube26 of the sootblower 16 may also be configured to rotate while the highpressure fluid 24 is discharged from the nozzles 28.

The boiler system 10 also includes one or more vibration measuringdevices 14 coupled to the boiler 12 to measure vibrations in the boilersystem 10. Exemplary vibration measuring devices 14 may include anaccelerometer, a displacement measurement device, a velocity measurementdevice and combinations thereof The vibration measuring devices 14 aremounted on strategic locations on the boiler support structure such ason the hanger rods 32 (FIG. 2), on the overhead beams 34 (shown in FIG.3), or at an exterior surface of the boiler 12 (FIG. 1), such as on aroof 38 of the boiler or in the penthouse (not shown). The vibrationmeasuring devices 14 collect vibration data, such as changes inamplitude and natural frequency, of the heat exchanger surfaces 48.

The system also includes a deposit detection device 18 that receivesinput for the vibration measuring devices 14 and optionally communicateswith the integrated device 30 that may control the operation of thesootblower 16. The deposit detection device 18 includes softwareconfigured to interpret vibration data received from the vibrationmeasuring devices 14 and to provide instructions to the integrateddevice 30, so as to direct operation of the sootblower 16 and the lancetube 26.

The sootblowers 16 are periodically operated to clean the heat exchangersurfaces 48 to restore desired operational characteristics. In use, alance tube 26 of a sootblower 16 moves relative to heat exchangersurfaces 48 through passages 50. The sootblowers 16 are inserted intoand extracted from the boiler 12 such that the nozzles 28 move between afirst position located outside of the boiler 12 and a second positionlocated inside the boiler 12. As the nozzle 28 on the lance tube 26 ofthe sootblower 16 move between the first and second positions, thenozzle 28 rotates adjacent the heatexchanger surfaces 48 such that thehigh pressure fluid 24 is expelled about a radius along the path of thenozzle 28 between the first and second positions. In an embodiment, thesecond position is the maximum inserted position. The sootblowers 16move generally perpendicularly to the heatexchanger surfaces 48 as thelance tubes 26 move through the passages 50.

The movement of the sootblower 16 into the boiler 12, which is typicallythe movement between the first and second positions, may be identifiedas a “first stroke” or insertion, and the movement out of the boiler 12,which is typically the movement between the second position and thefirst position, may be identified as the “second stroke” or extraction.Generally, sootblowing methods use the full motion of the sootblower 16between the first position and the second position; however, a partialmotion may also be considered a first or second stroke. The highpressure fluid is usually applied during both the first and secondstrokes.

As the sootblower 16 moves adjacent to the heat transfer surfaces 48,the high pressure fluid 24 is expelled through the openings in thenozzle 28. The impact of the high pressure fluid 24 with the deposits 20accumulated on the heat exchanger surfaces 48 produces both a thermaland mechanical shock that dislodges at least a portion of the deposits20. However, some amount of deposit 20 remains. As used herein, the term“removed deposit” refers to the mass of a deposit that is removed by thesootblowing procedure, and “residual deposit” refers to the mass of adeposit that remains on a heat exchanger surface 48 after a sootblowingcycle.

The impact of the high pressure fluid 24 on the heat exchanger surfaces48 causes vibration or a change in amplitude and frequency of the heatexchanger surfaces 48, which is detected and measured by the vibrationmeasuring devices 14. For purposes of the present invention, the term“vibration” refers to a periodic back-and-forth motion of an elasticbody or medium. The vibration is usually a result of the displacement ofa body from an equilibrium condition, followed by the body's response tothe forces that tend to restore equilibrium. The term “amplitude” refersto the maximum absolute value of a periodic curve measured along itsvertical axis. The greater the amplitude of the vibration, the greaterthe energy it carries. The term “frequency” refers to the number ofoscillations per second. Natural frequency is the frequency with which asystem oscillates in the absence of external forces.

As an amount of deposit 20 buildup changes on the heat exchangersurfaces 48, at least two things happens: 1) frequency of vibrations ofthe particular heat exchanger surface 48 changes and 2) the amount ofpressure applied by the high pressure fluid 24 delivered by the lancetube 26 to that particular heat exchanger surface 48 changes. Thevibration of the heat exchanger surface 48 can be analyzed to detect thepresence of residual deposits. In particular, the effect of residualdeposits on the amount of excitation energy transferred to the heatexchanger surface 48 by the high pressure fluid 24 can be evaluated aschanges in the vibration amplitude or frequency of the heat exchangersurfaces 48. The amount of energy excitation that the high pressurefluid 24 delivers to the heat exchanger surface 48 is a direct functionof or directly proportional to the amount of deposit 20 buildup on thecorresponding heat exchanger surfaces 48. In other words, increasedenergy excitation at the heat exchanger surface 48, as indicated bychanges in the vibration amplitude or frequency, signifies an increasein deposit 20 buildup on that heat exchanger surface 48.

The transmission of energy from the high pressure fluid 24 expelled fromthe sootblower 16 to the heat exchanger surface 48 is proportional tothe mass of deposit 20 buildup on the heat exchanger surface 48. Themass of the deposit 20 buildup on the heat exchanger surface 48 can beused to determine an amount of high pressure fluid 24 the sootblower 16needs to deliver to remove the deposits 20 from the heat exchangersurface 48. Aspects of the present invention are directed to analyzingthe changes in vibration amplitude and frequency responses in the boilersystem 10 produced by the forces transmitted from the high pressurefluid 24 expelled from the sootblower 16 to deposits 20 on the heatexchanger surfaces 48. Therefore, the concept of energy excitationresponse is used to determine the location and removal of the deposits20. The measured vibration may then be used to control a flowcharacteristic of the high pressure fluid 24, such as an amount of highpressure fluid 24 discharged from the nozzle 28 on the lance tube 26 ora flow rate of the high pressure fluid 24.

An aspect of the invention is directed to methods of mapping deposits 20on one or more heat exchanger surfaces 48 in a boiler system 10. Adeposit map is generally a spatial representation of the location ofeach sootblower 16 in the boiler 12 and the respective deposit 20buildup profile as determined by the path of the individual sootblower16 within the boiler 12. A deposit map may be generated by moving atleast one lance tube relative to at least one heat exchanger surfacewhile discharging a high pressure fluid 24. The high pressure fluid 24impacts deposits on the heat exchanger surfaces resulting in reactiveforces in the boiler system that may be measured to identify thepresence of a deposit. Thus, by incrementally and simultaneouslytranslating and rotating the nozzle 28 on the lance tube 26 at a setpenetration distance into the boiler 12, deposits 20 may be detected ata plurality of locations on the heat exchanger surfaces 48. The positionof the sootblower 16 relative to the heat exchanger surfaces 48 when adeposit is identified may then be used to determine the position ofidentified deposit along the path of the sootblower. The position ofdeposits 20 identified along the path of each sootblower 16 may be usedto generate a map of deposits at each sootblower 16 location. In anembodiment, the reactive forces are changes in vibration amplitude andfrequency measured in the boiler system 10 that are produced by forcestransmitted from the sootblower 16 to deposits 20 on the heat exchangersurface 48 by the high pressure fluid 24. Other reactive forces in theboiler system indicative of a deposit on the heat exchanger surface maybe used to generate deposit maps.

In an embodiment, the map may be represented as a table that identifiesthe sootblower 16 and the position along the path of the identifiedsootblower 16 where a deposit 20 is detected. The table may alsoidentify the relative location of the sootblower 16 in the boiler system10. In another embodiment, the map is a two dimensional representationof one or more deposits 20 on the heat exchanger surfaces 48 along thepath of a sootblower 16. In another embodiment, the map is a threedimensional representation of one or more deposits 20 on heat exchangersurfaces 48 along the paths of a plurality of sootblowers. Because aconventional boiler may have, depending on the size, from just a few tomore than one hundred sootblowers 16 located across the height and widthof the boiler 12, detailed maps of deposits 20 may be obtained.Successive deposit maps may change as the heat exchanger surfaces 48become fouled or is cleaned and relative changes in deposit 20 build upor position may be illustrated on the successive maps.

The generated maps may assist with identifying areas in the boilersystem 10 in which deposits 20 do not form, areas where the sootblowers16 are adequately removing deposits, and areas where residual depositsremain and that may require additional sootblower 16 activity to remove.These data may be used to develop an efficient sootblowing strategy thatreduces steam consumption for energy savings or improves heat exchangersurface 48 effectiveness. For example, a sootblower 16 could be operatedin “deposit 20 location mode” periodically, for example, once per day,and the collected information may be used to update a current depositmap. This map may be used to adjust the priority of sootblower 16operations for effective and efficient use of the sootblower 16 and toreduce steam consumption for energy savings.

Referring now to FIG. 4, a flow chart depicting a process 100 foranalyzing a signal from a vibration measuring device 14 is presented inaccordance with an embodiment of the invention. The analytical process100 includes a sequence of operations that may be performed by thedeposit detection device 18.

In block 102, a threshold for determining the presence of an eventindicative of a residual deposit on a heat exchanger surface 48 isestablished. The threshold is a value or a range of values against whichthe signal from the vibration measuring device 14 may be compared. Forexample, the threshold may be an amplitude at a given frequency or acalculated root mean squared (RMS) amplitude. In an exemplaryembodiment, the threshold is predetermined and can be based onhistorical data. The historical data can include data taken when theboiler is clean such as just after startup. In an alternativeembodiment, the threshold is determined based on real time or near realtime data from the vibration measuring device 14. In yet anotheralternative, the threshold is established as a multiple of the naturalfrequency or amplitude of the boiler system, and in particular that ofheat exchange surfaces.

In block 104, a signal from the vibration measuring device 14 isanalyzed for signals that exceed the threshold to establish theoccurrence of an event. The signal from the vibration measuring device14 corresponds to the frequency, the amplitude, or both the frequencyand amplitude of the vibration of the boiler system 10 at the locationof the vibration measuring device 14. An event may be identified as asignal from the vibration measuring device 14 that exceeds thethreshold. In an embodiment, the event is a signal that significantlyexceeds the threshold as determined by statistical analysis. In analternative embodiment, the event is a signal that exceeds the thresholdby a predetermine percentage.

In block 106, the location of the nozzle 28 is identified at theoccurrence of the event. In an embodiment, the location of the nozzlemay be identified by recording the time of the occurrence of the eventduring a stroke of the sootblower 16 and correlating that time with thelocation of the nozzle 28. Other methods of identifying the location ofthe nozzle 28 of the sootblower 16 at the occurrence of an event may beemployed, such as the use of rotational and displacement measurementsensors.

In block 108, the location of the nozzle at the occurrence of an eventis recorded as the location of a potential deposit.

The analytical process 100 set forth in FIG. 4 may be repeated for eachstroke of a sootblower 16 into and out of a boiler system. In anembodiment, the location of a potential deposit recorded in a firststroke is compared with the location of a potential deposit recorded ina second stroke. If the location of a potential deposit recorded in afirst stroke is near to or the same as the location of a potentialdeposited recorded in a second stroke, then the presence of a deposit atthe location may be considered to be confirmed. In some embodiments, thesootblower 16 does not follow the same helical path on the way into theboiler system as it does on the way out. In such embodiments, a depositrecorded in a first stroke might not be recorded for the second stroke.

FIG. 5 illustrates exemplary field data collected using two vibrationmeasuring devices 14 at opposite locations (locations I and II) in aboiler system during the operation of four sootblowers (A, B, C, and D).Location I was on the same side of the boiler as the entry point for thesootblowers and location II was on the opposite side of the boiler.

The bottom tracing in FIG. 5 illustrates the electrical current of themotor driving the rotation of the sootblowers 16 during operation.Spikes 53 reflect changes in electrical current of the motor duringoperation of the sootblowers 16 at regions A, B, C, and D that resultfrom increased resistance required to initiate rotation of the motor.With reference to the data collected from sootblower A, starting ataround time 16470 seconds, upward direction of arrows 52 denote theinsertion of lance tube 26 in region A between the heat exchangers 48and downward direction of arrows 54 denote the retraction of the lancetube 26. The height of each arrow 52, 54 denote the relative position ofthe nozzle 28 of the lance tube 26 inside the boiler 12. For example,the arrow 52 having the shortest height denotes partial insertion of thenozzle 28 and the arrow 52 in the lower panel having the greatest heightdenotes full insertion of the nozzle 28 into the boiler 12. Similarly,the arrow 54 having the shortest height denotes full retraction of thetip and the arrow 54 having the greatest height denotes full insertion.

The vibration measuring devices 14 at locations I and II measured themovement of the heat exchanger surfaces 48 as changes in amplitudeand/or frequency of the heat exchanger surfaces 48 during the movementof the lance tube in the boiler system for the removal and or detectionof deposits 20 on the heat exchanger surfaces 48.

Amplitude profile A′ illustrates RMS amplitude data over a largefrequency range collected by the vibration measuring device 14 atlocation I during the operation of a sootblower at location A. With theexceptions of a few weak and strong spikes 60, 62, the amplitudes of theprofile data are generally consistent in height. The consistent heightof the amplitudes indicates that the high pressure fluid 24 beingsprayed from the sootblowers 16 is not contacting substantial depositsattached to the surface of the heat exchangers 48, which may beinterpreted as meaning that the sootblower 16 is successfully removingthe deposits 20 from the surface of the heat exchangers 48. Theamplitude data also trends down during the insertion of the sootblower16 and trends up during extraction. Without being bound by a particulartheory, the downward trend suggests that the sootblower 16 is movingaway from the vibration detection device 14 and the upward trendsuggests that the sootblower 16 moving toward the vibration measuringdevice 14. The consistent amplitudes detected by the vibration measuringdevice 14 may be used to establish a real time or near real timethreshold. The threshold can also be established as further describedabove with respect to block 102 in FIG. 4. Amplitude signals that fallbelow the threshold may indicate that deposits are not building up onthe heat exchanger surface 48 or that deposits 20 are being efficientlyremoved and amplitude signals that exceed the threshold may indicate thepresence of a residual deposit 20 on the surface of heat exchanger 48that has not been efficiently removed. Thus, in an embodiment, thevibration data are analyzed to identify amplitudes that are greater thana threshold indicative of the presence of a deposit 20 on the surface ofthe heat exchanger 48. Spikes 60, 62 were greater than the threshold,which would indicate the potential presence of a residual deposit on thesurface of the heat exchangers.

Spikes 60, 62 may be interpreted as an anomaly resulting from rareoccasional sudden impact noise caused by various means such asinteraction between the heat exchangers 22 and the sootblowers 16 or afiring rate of the boiler 12. However, spikes 60, 62 occurringrepeatedly over a period of time while the nozzle 28 passes through acommon location may be indicative of high deposit 20 buildups at thecommon location. In this case, the spikes 60, 62 indicate that cleaningactions should be directed to those particular locations. When it isdetermined that a particular location is more prone to the buildup ofdeposits 20, the operator can schedule cleaning processes with specificsootblowers 16 to routinely clean those locations and, thus, improve theefficiency of the operation of the boiler system 10.

Referring now to vibration amplitude profile A″ and the vibrationmeasuring device 14 at location II, as shown in FIG. 5, it can be seenthat the amplitude profile A″ was relatively consistent, with theexception of a few small spikes. However, an interesting aspect of theamplitude profile A″ is that the vibration measuring device 14 at areaII was located on an opposite side of the boiler 12 at location A, andtherefore, the shape of the profile A″ is nearly reversed to that of theprofile A′. For example, the amplitude profile A′ is concave, while theamplitude or frequency profile A″ is convex. The shapes of the amplitudeprofiles differs because location I of vibration measuring device 14corresponds to area A of the boiler 12 on the same side of the boiler 12as the insertion point for the sootblower 16, but the vibrationmeasuring device 14 at location II was on the opposite side of theboiler 12 in area A. The same was true with respect to the sootblowers16 at locations B, C, and D in the boiler and their respective vibrationamplitude profiles (B′, B″), (C′, C″) and (D′, D″).

In practice, the heat exchangers 22 are divided into several zones, witheach zone having a number of sootblowers 16 and vibration measuringdevices 14 in communication with one another. The vibration measuringdevices 14 in each zone communicate with all of the sootblowers 16 inthat zone. This helps to ensure that the vibration signal will be pickedup by at least one of the vibration measuring devices 14 in that zone.

Another aspect of FIG. 5 is the presence of strong spikes 64, 66, 68, 70which may reveal important information to the operator of the boiler 12.At first, these spikes 64, 66, 68, 70 may be interpreted as an anomalyresulting perhaps from an earthquake or sudden impact of an object withthe sootblower 16. However, as noted above, when spikes occur repeatedlyat the same locations over a period of time during operation of thesootblower 16, the spikes are indicative of high deposit 20 buildups atthese particular locations. Assuming that the spikes 64 and 66 are theresult of high deposit 20 buildup, a flow characteristic from the nozzle28 on the sootblower lance tube 26 should be increased at that locationto remove the deposits 20. For example, the locations of the heatexchanger surfaces 48 associated with the spikes 64 and 66 may needlarger amounts of high pressure fluid 24 to remove the deposits 20, orthe high pressure fluid 24 may need to impact the heat exchangersurfaces 48 at those locations with an increased flow rate or with agreater force. In contrast, spikes 68 and 70 each only appear at onetime point on the in stroke for the sootblower 16 and do not appear onthe out stroke. These data suggest that potential deposits in these twolocations are being adequately removed by the existing protocol. Thesedata could also suggest that the path of the sootblower 16 on the instroke is slightly different from the path of the sootblower on the outstroke and that the deposits identified on the in path are notidentifiable on the out stroke.

Referring back to FIGS. 4 and 5, it should be noted that the frequencyor high pressure fluid output delivered by particular sootblowers 16 maybe adjusted in accordance with their respective vibration measurements.By reviewing the vibration differences in the heat exchangers 22 thatarea associated with individual sootblowers 16, or groups of sootblowers16, the boiler operator may develop an understanding of locations in theboiler 12 where the most deposit 20 buildup or fouling is occurring.This information may be used to establish the frequency of operation orhigh pressure fluid output delivered to particular sootblowers 16 forreducing fouling and improving boiler 12 efficiency by using only anamount of high pressure fluid 24 necessary to remove deposits 20. Theinformation may also be used to adjust boiler 12 conditions orconfigurations to reduce fouling at particular locations. For example,the information may be used to improve the design of the boiler 12 toreduce fouling or to identify locations within the boiler 12 foradditional or reduced fouling abatement mechanisms.

The deposit detection device 18 (FIG. 1) receives signals from thevibration measuring devices and may optionally control the operation ofthe sootblower lance tube 26 based on the deposits 20 located on one ormore of the heat exchanger surfaces 48. The deposit detection device 18also controls the amount of high pressure fluid 24 supplied or the highpressure fluid's 24 flow rate to the heat exchanger surfaces 48 duringcleaning portions of the insertion and extraction strokes and duringcooling portions of the insertion and extraction strokes when steam isused to keep the sootblower from overheating but not for cleaningpurposes. The deposit detection device 18 generally includes aprocessing unit and a memory device. The deposit detection device 18 maybe implemented as a computer (not shown) programmed to carry out thetasks described. The deposit detection device 18 may also be implementedusing hardware, software, or combinations thereof. The memory may beencoded with computer readable instructions that cause the processingunit to perform the data analysis described herein.

The deposit detection device 18 may communicate with the integrateddevice 30, which provides control signals to the sootblower lance tube26 to start and stop the sootblower 16 strokes. Accordingly, theintegrated device 30 may control the frequency of use of each of thesootblowers 16. The integrated device 30 may also provide signals to adata acquisition system (not shown) indicating when individualsootblowers 16, or groups of sootblowers 16, are at particular locationsof their strokes. For example, the integrated device 30 may provide asignal to the data acquisition system when a particular sootblower 16begins a stroke and when the particular sootblower 16 ends its stroke.Furthermore, the integrated device 30 may indicate the insertion andextraction portions of the stroke. The data acquisition system mayutilize the signals indicative of the beginning and the end of aparticular sootblower 16 stroke to identify vibration measurements fromthe vibration measuring device 14 occurring at or near the beginning andthe end of the sootblower 16 stroke. The deposit detection device 18 maythen implement statistical techniques to manipulate the amplitude orfrequency data associated with individual sootblowers 16 or groups ofsootblowers 16. The vibration characteristics such as the dynamicacceleration, velocity, or displacement data can be used to select asuitable frequency for operation of the sootblowers 16 or a highpressure fluid 24 output of the sootblowers 16.

The data acquisition system generally includes a processing unit and amemory device. The data acquisition system may be implemented as acomputer (not shown) programmed to carry out the tasks described. Thedata acquisition system may also be implemented using hardware,software, or combinations thereof. The memory may be encoded withcomputer readable instructions that cause the processing unit to performthe data analysis described herein. The data acquisition system may be astandalone device or part of the deposit detection devices 18 or theintegrated device 30. In some embodiments, the deposit detection device18, the integrated device 30, and the data acquisition system arecombined in a single unit. It is to be understood that the location andconfiguration of the deposit detection device 18 and the integrateddevice 30 are flexible in accordance with general computing technology.

By selecting frequencies or high pressure fluid 24 usage for individualsootblowers 16 or groups of sootblowers 16 based on their measuredperformance, the overall amount of the high pressure fluid 24 utilizedby the sootblowers 16 may be reduced and the effectiveness of thesootblowers 16 improved. This technique can improve the overallefficiency of the boiler 12, which may allow the boiler system 10 toconsume less fuel for the same high pressure fluid 24 output or tooperate longer without shutdown (scheduled or unscheduled) due toplugging.

With reference back to FIG. 2, in another embodiment, vibrationmeasuring devices 14 may be used to detect release of a deposit 20 froma heat exchanger surface 48. One or more vibration measuring devices 14are coupled to a boiler 12, for example at a floor 40 of the boiler, ona hanger rod 32, or on a roof 38 of the boiler. The vibration measuringdevices 14 may comprise accelerometers, for example. When the deposit 20grows to a substantial mass, the deposit 20 may release from (or falloff of) the heat exchanger surface 48. This released deposit 80 iscommonly referred to as a clinker. When the deposit 20 releases from theheat exchanger surface 48, the vibration of the heat exchanger surface48 at the location from which the released deposit 80 falls changes,such as from a reactive force in the heat exchanger surface cause by therelease of the mass of the deposit from the surface. In this way, when avibration measuring device 14 coupled to the hanger rod 32 or the boilerroof 38 detects the vibration caused by the released deposit 80, thedetected vibration indicates the location from which the releaseddeposit 80 fell. In addition, the greater the vibration measured by thevibration measuring device 14 in response to release of the releaseddeposit 80, the greater the size of the released deposit 80.

Alternatively, a vibration measuring device 14 may detect the vibrationof boiler components resulting from impact of the released deposit 80with the boiler floor 40 or with other structures in the boiler systemimpacted by the released deposit as it falls. As the released deposit 80will tend to fall straight down if unobstructed, the vibration measuringdevice 14 that detects the strongest vibration will indicate a generalarea of the heat exchanger surfaces 48 from which the released deposit80 fell.

This embodiment of detecting released deposits 80 may be used separatelyor in conjunction with the method described above to monitor theaccumulation of deposits 20 on the heat exchanger surfaces 48. Forexample, the presence of released deposits 80 may indicate that aparticular location on the heat exchanger surfaces 48 accumulates adeposit 20 more rapidly than other locations on the heat exchangersurfaces 48 or that a particular sootblower 16 is not cleaning aseffectively as other sootblowers 16.

While the present invention has been illustrated by the description ofspecific embodiments thereof, and while the embodiments have beendescribed in considerable detail, it is not intended to restrict or inany way limit the scope of the appended claims to such detail. Thevarious features discussed herein may be used alone or in anycombination. Additional advantages and modifications will readily appearto those skilled in the art. The invention in its broader aspects istherefore not limited to the specific details, representative apparatusand methods and illustrative examples shown and described. Accordingly,departures may be made from such details without departing from thescope or spirit of the general inventive concept.

What is claimed is:
 1. A boiler system comprising: a boiler having atleast one heat exchanger, the at least one heat exchanger having asurface on which a deposit may form; at least one retractable sootblowerhaving a lance tube for carrying a high pressure fluid into the boiler,the lance tube being configured to discharge the high pressure fluidsuch that the high pressure fluid impacts the heat exchanger surface toeffect a vibration thereof; and at least one vibration measuring devicecoupled to the boiler, the vibration measuring device being configuredto measure the vibration of the heat exchanger surface, wherein themeasured vibration of the heat exchanger surface indicates presence orabsence of the deposit on the heat exchanger surface.
 2. The boilersystem of claim 1, wherein the measured vibration of the heat exchangersurface indicates at least one of a location of the deposit or an amountof the deposit on the heat exchanger surface.
 3. The boiler system ofclaim 1, further comprising: at least one boiler supporting structurefrom which the at least one heat exchanger is suspended, wherein the atleast one vibration measuring device is coupled to the at least oneboiler supporting structure.
 4. The boiler system of claim 1, whereinthe boiler supporting structure is selected from the group consisting ofa hanger rod, an overhead beam, and combinations thereof.
 5. The boilersystem of claim 1, wherein the at least one vibration measuring deviceis coupled to an exterior surface of the boiler.
 6. The boiler system ofclaim 1, wherein the at least one vibration measuring device is selectedfrom the group consisting of an accelerometer, a displacementmeasurement device, a velocity measurement device and combinationsthereof.
 7. A method of detecting a deposit on at least one heatexchanger surface disposed within a boiler system, the methodcomprising: moving a lance tube relative to the at least one heatexchanger surface; impacting the at least one heat exchanger surfacewith a high pressure fluid discharged from the lance tube; measuring avibration in the boiler system caused by the impact of the high pressurefluid at a location on the at least one heat exchanger surface; andanalyzing the measured vibration to detect the presence of the depositat the location.
 8. The method of claim 7, further comprising:controlling a flow characteristic of the high pressure fluid dischargedfrom the lance tube at the location of the at least one heat exchangerin response to the measured vibration.
 9. The method of claim 8, whereinthe flow characteristic is selected from the group consisting of anamount of high pressure fluid discharged from the lance tube, a flowrate of the high pressure fluid, and combinations thereof.
 10. Themethod of claim 7, wherein the step of measuring a vibration furthercomprises: measuring vibrations in the boiler system caused by theimpact of the high pressure fluid with the at least one heat exchangersurface at each of a plurality of locations, wherein the step ofanalyzing the measured vibration further comprises analyzing themeasured vibrations from the plurality of locations on the at least oneheat exchanger surface, the method further comprising: generating a mapof the locations of any detected deposits on the at least one heatexchanger surface.
 11. The method of claim 10, further comprising:controlling a flow characteristic of the high pressure fluid dischargedfrom the lance tube while moving the lance tube relative to the at leastone heat exchanger surface based on the map of detected deposits. 12.The method of claim 11, wherein the flow characteristic is greater for alocation of the at least one heat exchanger surface having a greateramount of deposit than for a location of the at least one heat exchangersurface having a lesser amount of deposit.
 13. The method of claim 7,wherein the vibration is measured with at least one accelerometercoupled to the boiler.
 14. The method of claim 7, wherein the impactingof the at least one heat exchanger surface with high pressure fluidremoves at least a portion of the deposit at the location on the atleast one heat exchanger surface, the method further comprising:measuring a first vibration at a first time point caused by the impactof the high pressure fluid at the location of the at least one heatexchanger surface; measuring a second vibration at a second time pointcaused by the impact of the high pressure fluid at the location of theat least one heat exchanger surface; and comparing the first vibrationto the second vibration to determine changes in the amount of thedeposit on the at least one heat exchanger surface at the location. 15.The method of claim 7, wherein the greater the measured vibration at thelocation on the at least one heat exchanger surface, the greater anamount of the deposit at the location on the at least one heat exchangersurface.
 16. A process for analyzing a surface of a boiler, the processcomprising: passing a lance tube through the boiler in a first passeffecting a vibration therein; receiving a first signal indicative of avibration of a surface of the boiler; and in response to the vibrationexceeding a threshold, determining the existence of a deposit on thesurface of the boiler.
 17. The process of claim 16, further comprising:identifying the position of the lance tube when the vibration exceedsthe threshold; and determining a position of the deposit in the boilerbased on the position of the lance tube when the vibration exceeds thethreshold.
 18. The process of claim 16, further comprising: passing alance tube through the boiler in a second pass subsequent to the firstpass; receiving a second signal indicative of a second vibration of thesurface of the boiler; and in response to the second vibration exceedingthe threshold, determining the existence of a deposit on the portion ofthe boiler.
 19. The process of claim 18, further comprising: determininga position of the deposit in the boiler identified in the first pass;determining a position of the deposit in the boiler identified in thesecond pass; and comparing position of the deposit from the first passwith the position of the deposit from the second pass.
 20. The processof claim 19, further comprising comparing the first signal with thesecond signal if the position of the deposit from the first passoverlaps with the position of the deposit from the second pass, whereina difference between the first and second signals indicates a change inmass of the deposit on the portion of the boiler.
 21. A method ofmapping the location of one or more deposits on one or more heatexchanger surfaces in a boiler system comprising: moving at least onelance tube relative to at least one heat exchanger surface; impacting adeposit on the at least one heat exchanger surface with a high pressurefluid discharged from the at least one lance tube; measuring a reactiveforce in the boiler system caused by the high pressure fluid impactingthe deposit to identify the presence of a deposit; identifying theposition of the deposit in the boiler system; and generating a map ofthe deposit in the boiler system based on the identified position of thedeposit.
 22. The method of claim 21 wherein the at least one lance tubeis a plurality of lance tubes and the at least one heat exchangersurface is a plurality of heat exchanger surfaces.
 23. The method ofclaim 21 wherein the reactive force produces vibration that exceeds athreshold.
 24. A method of detecting a deposit released from a surfaceof a heat exchanger in a boiler, the method comprising: providing atleast one vibration measuring device coupled to the boiler; detecting avibration caused by at least one of a release of the deposit from thesurface of the heat exchanger or the impact of the released deposit witha surface in the boiler system, the vibration being detected by the atleast one vibration measuring device; and analyzing the detectedvibration to determine at least one of the location on the surface ofthe heat exchanger surface from which the deposit was released or thelocation in the boiler system impacted by the deposit.
 25. The method ofclaim 24, wherein the at least one vibration measuring device is coupledto a floor of the boiler and detects the vibration caused when thereleased deposit impacts the floor of the boiler.
 26. The method ofclaim 24, wherein the at least one heat exchanger is suspended from aboiler supporting structure, wherein the at least one vibrationmeasuring device is coupled to the boiler supporting structure andmeasures the vibration of the heat exchanger caused when the depositreleases from the surface of the heat exchanger.
 27. The method of claim24, wherein the at least one vibration measuring device is anaccelerometer.